"AN IMPROVED PROCESS FOR PREPARTION OF GLYCIDYL AZIDE PREPOLYER"

Abstract

This indention relates to an improved process for the preparation of g1ycidyl, azide prepolymer and wherein according to this invention the condensation of sodium azide and ethylene glycol is carried out in an organic polar solvent such as 1,1,1-trichlcroethane and subsequently the same is reacted with epichlorohydrine,

Full Text

This invention relates to an improved process for preparation of glycidyl azide prepolymer.
The azide polymers, more particularly glycidyl azide prepolymer are used as binder plasticiser for the fuel rich propellant formulations.
The glycidyl azide prepolymer helps to improve the combustion efficiency, essential for the production of fuel rich gases in the primary chamber of the rocket.
Yet another advantage of glycidyl azide prepolymer in the fuel rich propellant formulation is that it replaces the non-energetic plasticiser and inturn this results in pyrolyzability of formulations because the glycidyl azide prepolymer undergoes exothermic decomposition particularly on the formulation surface resulting in considerable increase in surface temperature, as described in our copending patent application no. 2391/Del/95.
Still another advantage of glycidyl azide prepolymer in fuel rich propellant formulations is to desensitise the double base matrix in the said formulation as described in our copending patent application no. 2391/Del/95.
The azide polymers, more particularly glycidyl azide prepolymer are prepared by two steps or multisteps process, comprising of synthesis of intermediate and are extracted in the dimethyl formamide solvent medium.
The existing methods for the preparation of glycidyl azide prepolymer suffer from
the disadvantages, viz:-:3 :
i) The removal of solvent, i.e dimethyl formamide is difficult and time
consuming and results in the impurity of the glycidyl azide prepolymer ii) The existing methods are two step or multistep processes, hence,
iii) The yield and purity of the glycidyl azide prepolymer is not good.
An object of the present invention is to propose an improved process for the preparation of azide polymers, more particularly glycidyl azide prepolymer and product thereof.
Another object of the present invention is to propose an improved process for the preparation of glycidyl azide prepolymer which avoids the preparation and isolation of intermediates by avoiding two or multistep process.
Still another object of this invention is to propose an improved process for the preparation of glycidyl azide prepolymer wherein the removal of solvent like diemthyl formamide is avoided and extraction of final product is made easier.
A further and main object of the present invention is to propose an improved process for the preparation of glycidyl azide prepolymer and product thereof which in turn is one-step process and is carried out in the same reaction vessel.
Still further an object of the presently disclosed invention is to propose an improved process, which results in the good yield of glycidyl azide prepolymer and in good purity.
According to this invention, there is provided an improved process for preparation of glycidyl azide prepolymer comprising the steps of (a)reacting 1 part by weight of ethylene glycol with 2 parts by weight of 1, 1, 1 trichloroethane in a reaction chamber fitted with a magnetic stirrer and heater, heating the reaction mixture to 65 to 75°C for about 1 hour: (b)adding epichlorohydrine (ECH) to the said reaction mixture drop by drop in ratio of 1 part by weight of ECH to 1 part by weight of ethylene glycol, stirring the mixture, raising the temperature of the said reaction mixture to 80 to 85°C and maintaining this temperature for 15 to 20 hours; (c) cooling the said reaction mixture to ambient temperature and extracting glycidyl
azide prepolymer with dichloromethane in the ratio of 300 ml of dichoromethane to each mole of ethylene glycol at ambient temperature, washing the resulting product with water: (d) drying the resulting product of step (c) over sodium sulphate at ambient temperature in the ratio of 100 g of sodium sulphate to 1 mole of eythlene glycol to obtain dry glycidyl azide prepolymer.
According to the proposed improved process of the present invention the condensation is carried out at temperature of 65-75°C, while stirring the reaction mixture. The temperature of the reacting mixture is raised to 80 -85°C after complete addition of epichlorohydrin According to the preferred embodiment of this invention the epichlorohydrin is added drop by drop through the separating funnel and the temperature of 80-85°C is maintained for time of 15-20 h.
The resulted reaction mixture, is allowed to cool to the ambient temperature and the final product that is, glycidyl azide prepolymer is extracted with dichloromethane. The unreacted salts and ethylene glycol and other water soluble impurities, which are left after extraction from organic solvent that is dichloromethane are removed, according to the process of the present invention by washing the product with water. The excess of water contents in the final product are removed by known procedure preferably by drying over sodium sulphate.
The presently proposed improved process is further characterised by the ease of operation, good yield and purity of glycidyl azide prepolymer with molecular weight varying from 350 to 500.
The invention is illustrated, but hot limited by the following examples.
Example
The glycidyl azide prepolymer was synthesised according to the proposed improved process of the present invention, as described here in above, in one litre, three necked, round bottom reaction vessel with provisions of thermometer, water condenser and a separating funnel, and placed on water bath. The reaction vessel alongwith water bath is placed on a heater provided with magnetic stirrer. 1 mole of each of sodium azide and ethylene glycol, and 500 ml of 1,1,1- trichloroethane are added in the reaction vessel through one neck, which is latter on fitted with thermometer. The water condenser is placed in appropriate neck after adding the magnetic bead in the reaction vessel. The separating funnel filed with one mole of epichlorohydrin is placed in the third neck. The reaction mixture in the vessel is allowed to heat up to the temperature of 75°C After about 1 h the epichlorohydrine is added through separating funnel essentially drop by drop. After the complete addition of epichlorohydrine the temperature of the reaction mixture is allowed to raise to 80° C and the temperature of 80°C is maintained for 16 h. Then the reacted mixture is treated according to the described process. The glycidyl azide prepolymer is extracted from mixture by dichloromethane, thoroughly washed with water and dried over sodium sulphate over night.
The qualitatively the glycidyl azide prepolymer was analysed by infra-red spectroscopy and the data confirms formation of pure glycidyl azide prepolymer. The molecular weight of the prepolymer is 450
Example 2
The reaction was carried out with double amount of reactants as described in the example 1 above. The molecular weight of the resulted product was 480.

WE CLAIM
1. An improved process for preparation of glycidyl azide prepolymer
comprising the steps of:
(a) reacting 1 part by weight of ethylene glycol with 2 parts by weight of 1, 1, 1 trichloroethane in a reaction chamber fitted with a magnetic stirrer and heater, heating the reaction mixture to 65 to 75°C for about 1 hour;
(b) adding epichlorohydrine (ECH) to the said reaction mixture drop by drop in ratio of 1 part by weight of ECH to 1 part by weight of ethylene glycol, stirring the mixture, raising the temperature of the said reaction mixture to 80 to 85°C and maintaining this temperature for 15 to 20 hours;
(c) cooling the said reaction mixture to ambient temperature and extracting glycidyl azide prepolymer with dichloromethane in the ratio of 300 ml of dichloromethane to each mole of ethylene glycol at ambient temperature, washing the resulting product with water;
(d) drying the resulting product of step (c) over sodium sulphate at ambient temperature in the ratio of 100 g of sodium sulphate to 1 mole of eythlene glycol to obtain dry glycidyl azide prepolymer.
2. An improved process for preparation of glycidyl azide prepolymer as
substantially herein described and illustrated.